March 1, 2012

Understand Your Nitrogen Source​

Nitrogen is one of those inputs necessary for maximum corn production, but its best use can be elusive for some managers. The different forms that are available and the variety of products it can be used with, can sometimes make it difficult to manage potential nitrogen loss. Most producers want to manage nitrogen in a way that maximizes production, limits environmental impact, and is cost-effective.

In order to do that, it is necessary to understand the common forms that can be applied and the forms nitrogen can take when in the soil.

One fact is common among all sources: Nitrogen either ends up in the ammonium (NH4+) form or the nitrate (NO3–) form. The ammonium form remains bonded to clay soil particles due to its charge and therefore is the most stable form in the soil. However, apply ammonium to the surface and it has the potential to volatilize into the atmosphere. Even if properly placed in the soil, the ammonium is still subject to loss.

As nitrosomonas bacteria convert the ammonium to nitrate, it becomes more at risk for loss. Loss from the nitrate form can occur in two ways. One is denitrification, or the removal of oxygen from the soil profile. As the soil remains saturated, oxygen is depleted and nitrogen is then lost into the atmosphere. This process is made faster by time and warmer temperatures. The other common way to lose nitrate is through leaching. Since nitrate is in a negative form, it does not bond tightly with the soil. Therefore it is subjected to movement down through the profile. If there is not enough uptake by the plant or the nitrate is leached below the root zone, nitrogen can become limiting in the future development of the crop.

The safest way to maximize nitrogen efficiency is to apply nitrogen in the right form at the right time, making sure that you have utilized the right rate with the right source. Easy for me to say, but essentially that is the movement behind nitrogen management or a 4R approach. It is the best way to minimize production risk and maintain the level of freedom we enjoy with our nitrogen applications. Table 1.1 outlines the most common sources of nitrogen, the form they take, and how that form could be lost.

N types, soil form, & loss

While the above are the most common forms used, there are many inhibitors that can limit the risk for loss due to volatility or conversion to nitrate. The various inhibitors on the market are designed ultimately to slow the conversion process to nitrate, therefore keeping the nitrogen in the safer ammonium form. Table 1.2 outlines the most common inhibitors and their potential benefits. Consider using an inhibitor whenever possible to minimize your risk for loss and improve your chances of keeping nitrogen available for the growing corn crop.

nitrogen loss inhibitors comparison

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